It is stated that some specific craniofacial characteristics are associated with obstructive sleep apnea syndrome (OSAS). In an attempt to test this hypothesis cephalometric radiographs have been used to record craniofacial measurements. A pilot study conducted in our laboratory compared the craniofacial characteristics of ten OSAS subject (AHI>50) and ten heavy snorers (AHI 10-20) matched on age, height, and weight. We found that hyoid bone position and tongue length were significantly (p<004) different between OSAS and snorers. In addition, head and facial form, cranial base alignment, posterior airway space, ramus width relative to the middle-cranial fossa, and sagittal tongue area relative to intermaxillary area had a definite trend towards significance (p<05). The positive results obtained from the pilot study has prompted us to submit this proposal. The present study will be conducted in two phases: Phase I will be aimed at constructing a craniofacial index score (CIS) using cephalometric and anthropometric measurements form 60 OSAS and 60 Snoring subjects (testing sample). A separating boundary (CIS) will be established using discriminant and logistic analyses to differentiate between the two groups. Phase II will test the validity of the CIS using a separate sample of 60 OSAS and 60 Snores (diagnostic sample). The diagnostic sample will be classified by means of the CIS developed during Phase I. Sensitivity and specificity of the CIS will be determined and compared to the "gold standard" of polysomnography and clinical diagnosis. All measurements in both Phases will be determined by an investigator blinded to the subject's clinical diagnosis. Construction of the CIS may be a useful adjunct diagnostic procedure to identify individuals predisposed to OSAS. It is hoped that this diagnostic tool may be used in place of more costly and invasive MRI or CT scans.